1. Field of the Invention
The herein disclosed invention relates to an apparatus for mechanically creating and breaking optical connections between a first set of optical fiber ends and a second set of optical fiber ends.
2. Prior Art
Fiber optic technology is finding increasing application in industry. This technology offers an alternative information transmission medium which is increasingly surplanting use of microwave waveguides, radio frequency coaxial cables, etc. where a high bandwidth, reliable transmission link must be established. Optical fibers provide a transmission medium for electromagnetic radiation in the visible and near-visible light region of the electromagnetic frequency spectrum. Since such frequencies are substantially higher than those in the radio wave and microwave portion of the electromagnetic spectrum, a greater amount of information may be transferred via an optical fiber due to the higher information bandwidth possible at such frequencies.
Optical fibers are light-transparent glass threads typically having a diameter of 0.01 inch or less. Two major problems with fiber optical technology have been to provide low-cost, effective devices for semipermanently connecting the ends of optical fibers together, and to provide a low-cost, effective devices for switching an optical fiber from optical alignment with one optical fiber to optical alignment with another optical fiber.
With respect to the problem of providing suitable connectors for optical fibers, U.S. Pat. No. 4,087,155 entitled "Single Optical Fiber Connectors Utilizing Spherical Alignment Elements" to G. R. Deacon teaches an optical fiber connector formed by three mutually contacting spheres and the resulting interstitial spaced formed. Other U.S. Patents such as U.S. Pat. No. 4,050,783 entitled "Connectors for An Optical Fiber Link" to A. Tardy, U.S. Pat. No. 3,989,567 entitled "Connective Method for Two Optical Fibers having the Same Diameter" to A. Tardy, and U.S. Pat. No. 4,056,305 entitled "Single Optical Fiber Connector Utilizing Elastomeric Alignment Device" to R. MCCartney, et al. also teach various optical fibers positioned in an interstitial space formed by three mutually contacting elements having a circular cross-section. However, none of these patents teach the biasing of two optical fiber retainers, each possibly holding a plurality of optical fibers, against each other in a plurality of mechanically stable alignment positions and a switching mechanism to controllably move one retainer with respect to the other to cause switching of the optical connections formed, thereby forming an optical fiber relay.
The general problem of providing a relay apparatus for use with fiber optic technology has been an especially difficult problem. In order to create a optical connection between two optical fibers, the ends of the optical fibers must be in precise alignment. Not only must the ends of the optical fibers be in extremely close proximity or touching each other, but also the ends cannot be offset with respect to each other since any angular offset drastically hinders the transfer of a light signal from one optical fiber to another. Due to the small diameter of optical fibers it has been a significant technological problem to provide a simple, low-cost, low-loss switchable connection between optical fibers.
One approach to the problem has been to provide two plates sliding across each other between fixed positions. Each optical fiber end would be inserted through the back of one of the two plates to the surface of the plate in contact with the other plate. The optical fiber ends which are desired to be in optical alignment would be inserted into the plates at a position which would bring them into optical alignment at the desired fixed position of the plates. As one of the plates would slide across the other to one of its alternate fixed positions, a previously made optical connection would be broken and a new one could be created. Such an apparatus, although mechanically possible, requires a large number of high precision components. A method for fixing to a high degree of accuracy the alignment positions of the plates with respect to each other must be assured. Additionally a high precision method for precisely securing the ends of the optical fibers is also required. Environmental factors such as temperature and shock may adversely affect the critical alignment necessary to such a relay apparatus, creating a finicky and unreliable device.
Another method for providing a fiber optics relay apparatus is by use of a light-transparent crystal having an index of refraction which may vary in accordance with a voltage applied across it. By appropriate positioning of the optical fiber ends against the crystal, the light emitted from one optical fiber can, by adjustment of the crystal's index of refraction, by directed to one or more optical fibers, creating an electronically controlled fiber optic relay. The chief advantage of such a scheme is that the switching of the information from an optical fiber is electronically controlled since the index of refraction is determined by the voltage applied across the crystal. Accordingly, the information obtained from an optical fiber can be switched at a high rate of speed.
A major disadvantage of such a fiber optics relay apparatus is the signal being switched suffers a significantly large loss, e.g. 20 db or greater, due to the insertion of a crystal which has an index of refraction different from that of the optical fibers. In addition, additional losses are caused by impurities in the crystal, and by unavoidable diffusions, refractions, and reflections of the light signal within the crystal.
It is an object of the herein disclosed invention to provide a mechanically simple fiber optics relay which requires a minimum of high precision machining. It is a further objective of the herein disclosed invention to provide a low loss optical connection between two sets of optical fibers. Additionally, it is an objective to provide any switching configuration desired from single pole, single throw to multiple pole, multiple throw. It is also desired to provide a fiber optics relay apparatus which may be switched manually, electronically, hydraulically, or via any other desired control mechanism. Another objective of the invention is to provide a fail safe switching mechanism for the relay apparatus so that a failure of the switching control mechanism, e.g., power failure, will cause the relay apparatus to revert to a well-defined configuration, allowing for the optical connection of the optical fibers.